Anytime you shop online (or instore), you should look out for promo codes. Last week, I found hollisterco promo code for 20% off. I know right, they never have coupon codes since they don't have a box for the code....well, they did and it worked. Oh sorry, getting away from the subject of makeup. So when you shop for makeup, you should also look for promo codes. The best place that I like to start is google. Just type in the brand + promo code. Most likely, you will end up on retailmenot.com. That's actually a good site to use and I often end up on that site anyway and you can tell if the code is still active or not...etc. 

So try it out and here are just some brands:

http://www.retailmenot.com/view/urbandecay.com
http://www.retailmenot.com/view/eyeslipsface.com
http://www.retailmenot.com/view/everydayminerals.com
http://www.retailmenot.com/view/clinique.com
http://www.retailmenot.com/view/prescriptives.com
http://www.retailmenot.com/view/sephora.com

You get the idea... always worth a try before you buy something because you can end up saving some money!